It is desirable to diagnose a short-circuit to a battery and/or a ground of an air-fuel sensor in an automotive application. A wide-range air-fuel sensor typically has several electrical wires that may become short-circuited to the battery or ground. Difficulty in determining which sensor wire is short-circuited may be caused by the internal cell bias voltage from the reference and pump cells, battery and ground voltage fluctuations, and large common-mode signals. Additionally, it is advantageous to be able to pinpoint a short-circuit while the sensor is at operating temperature, of which the prior art is incapable.